Init: Quick and dirty

.gitignore

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+configs/*
+cmd/tt/tt

README.md

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+Tiny DDNS service I wrote because I needed to move VPS  and did not want to use the old one written in Python.

build/app/Dockerfile

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+FROM golang:1.16.2
+
+ENV GO111MODULE=off
+RUN go get -u -d g.phga.de/phga/dd/...
+WORKDIR /go/src/g.phga.de/phga/dd/cmd/dd
+RUN go build
+CMD ["./dd"]

build/docker-compose.yml

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+version: '3'
+
+services:
+  dd:
+    build:
+      context: ./app
+      dockerfile: Dockerfile
+    restart: 'always'
+    ports:
+      - 8000:6969
+    volumes:
+      - /srv/dd/configs:/go/src/g.phga.de/phga/dd/configs

cmd/dd/config.go

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+package main
+
+import (
+	"encoding/json"
+	"log"
+	"os"
+)
+
+type Config struct {
+	WebPort        string                       `json:"web_port"`
+	WebDomain      string                       `json:"web_domain"`
+	WebAdmin       string                       `json:"web_admin"`
+	WebAdminPass   string                       `json:"web_admin_pass"`
+	MailUser       string                       `json:"mail_user"`
+	MailPass       string                       `json:"mail_pass"`
+	MailSmtpServer string                       `json:"mail_smtp_server"`
+	MailSmtpPort   string                       `json:"mail_smtp_port"`
+	DdUsers        map[string]map[string]string `json:"dd_users"`
+	DnsTTL         int                          `json:"dns_ttl"`
+}
+
+var config Config
+
+func init() {
+	f, err := os.Open("../../configs/config.json")
+	if err != nil {
+		log.Fatalln(err, "Could not read config file")
+	}
+	defer f.Close()
+	err = json.NewDecoder(f).Decode(&config)
+	if err != nil {
+		log.Fatalln(err, "Could not decode config file")
+	}
+}

cmd/dd/dd.go

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+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// https://dd.phga.de/dd?usr=<username>&pw=<passwd>
+func main() {
+	// cheap routing
+	http.HandleFunc("/dd", handleDynamicUpdate)
+
+	log.Fatalln(http.ListenAndServe(":"+config.WebPort, nil))
+}
+
+func handleDynamicUpdate(w http.ResponseWriter, r *http.Request) {
+	up := r.URL.Query()
+	ip := r.Header.Get("X-FORWARDED-FOR")
+
+	if len(ip) < 1 {
+		ip = strings.Split(r.RemoteAddr, ":")[0]
+	}
+
+	if len(up) != 2 {
+		log.Println("Attempted update for:", ip)
+		log.Println("Not enough arguments provided:", up)
+		return
+	}
+
+	for k, v := range config.DdUsers {
+		if k == up["usr"][0] {
+			if v["password"] == up["pwd"][0] {
+				log.Println("Starting update for:", ip, "(", v["domain"], ")")
+				// Do the update via nsupdate
+				err := updateDnsRecord(v["domain"], ip, v["hmac"], v["keyname"], v["secret"])
+				if err != nil {
+					log.Println("nsupdate failed:", err)
+				} else {
+					log.Println("nsupdate succeeded!")
+				}
+			} else {
+				log.Println("Wrong Secret provided!")
+			}
+		}
+	}
+
+}
+
+func updateDnsRecord(domain string, ip string, hmac string, keyname string, secret string) error {
+	f, err := os.Create("/tmp/update.dns")
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	update := fmt.Sprintf(`server 127.0.0.1
+                           key %s:%s %s
+                           update add %s %d a %s
+                           send`, hmac, keyname, secret, domain, config.DnsTTL, ip)
+
+	_, err = io.WriteString(f, update)
+	if err != nil {
+		return err
+	}
+	err = f.Sync()
+	if err != nil {
+		return err
+	}
+
+	nsupdate := exec.Command("nsupdate", "/tmp/update.dns")
+	out, err := nsupdate.Output()
+	log.Println(string(out))
+	return err
+}

go.mod

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+module g.phga.de/phga/dd
+
+go 1.16